Field of the Invention
The present invention relates to an expansion apparatus for recovering waste heat and a waste heat recovery system including the same. More specifically, the present invention relates to an expansion apparatus for recovering waste heat, the expansion apparatus being configured for stably producing electrical energy and/or mechanical energy irrespective of the flow rate of working fluid supplied from a boiler of a waste heat recovery system, and relates to a waste heat recovery system including the same.
Description of Related art
Internal combustion engines have been widely used in vehicles, ships, small generators, and the like, and many attempts have been made constantly to increase efficiency of internal combustion engines. Internal combustion engines discharge a large amount of heat as waste heat, and waste heat recovery systems have been developed to recover waste heat as energy and increase the overall efficiency of internal combustion engines.
These waste heat recovery systems are configured to recover waste heat from internal combustion engines as energy, convert the recovered energy into electrical or mechanical energy, and supply the converted electrical or mechanical energy to the internal combustion engines, accessories, or the like of the vehicles.
The waste heat recovery systems have a Rankine cycle to effectively recover waste heat from an internal combustion engine. The Rankine cycle includes a circulation path through which working fluid circulates, and has a boiler (evaporator), an expander, a condenser, and a pump along the circulation path of the Rankine cycle. The boiler (evaporator) heats and evaporates the working fluid by use of waste heat from the internal combustion engine (heat in exhaust gas and/or heat in EGR gas). The expander expands the high-temperature and high-pressure working fluid supplied from the boiler. The condenser condenses the working fluid discharged from the expander. The pump is located in the circulation path to circulate the working fluid.
The expander includes a housing and an expander wheel that is rotatable within the housing, and the expander wheel is rotated by the high-temperature and high-pressure working fluid supplied from the boiler. When the expander wheel is rotated by the high-temperature and high-pressure working fluid, rotational energy is generated and then transferred to a motor-generator or the crankshaft of the internal combustion engine to generate electrical or mechanical energy.
However, the flow rate of the working fluid supplied from the boiler to the expander may vary depending on an operating condition of the internal combustion engine, and thus the expander may not regularly generate rotational energy.
In addition, since the conventional expander has a structure in which the RPM of the expander wheel is increased, efficiency in generating rotational energy may not be substantially improved.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.